The present invention relates generally to a temperature-conditioned container for a vehicle and, more particularly, to a temperature-conditioned container with a power control module that regulates the energizing of a temperature-conditioning assembly. The present invention also relates to a defrost arrangement for use with coolers/refrigerators generally used in trucks or other vehicles.
There is an increasing interest in providing vehicles such as cars and trucks with containers in which items may be heated or cooled. It has been suggested that it is desirable to provide this type of container in a vehicle between the driver""s seat and the adjacent front passenger""s seat. An advantage of providing this type of container is that the persons in the vehicle will have ready access to food and beverage items that are maintained at a desirable temperature. Providing a driver with ready access to these items may lessen the extent to which the driver will divert his/her attention from the road and the state of the vehicle.
There are proposals to warm or cool the insides of these containers with heat pumps formed out of solid-state electrical components. In certain of these components, a thermal energy transfer effect, known as the Peltier effect, causes the assemblies with which they are integral, to function as heat pumps. One such heating/cooling assembly has been proposed in which a thermally conductive piece of metal is disposed inside the container to be warmed/cooled. This component is referred to as a heat exchanger. A section of the heat exchanger is coupled to a thermal energy pump or exchanger that is formed from a set of these solid-state components. A set of cooling fins, located outside of the container, are also coupled to the thermal energy exchanger. When the container is to be cooled, current is applied to the electrical components (forming the thermal energy exchanger) so that the exchanger functions as a heat sink to remove thermal energy from the container. The thermal energy removed from the container is transferred to the cooling fins. A fan, also part of the temperature-conditioning assembly, blows air across the cooling fins to foster the convective transfer of heat away from the fins. A more complete disclosure of containers of this design may be found in commonly owned U.S. Pat. No. 6,282,906 issued Sep. 4, 2001, entitled MOBILE VEHICLE TEMPERATURE CONTROLLED COMPARTMENT, which is incorporated herein by reference.
It is anticipated that the above-described assembly will be energized by the DC power supply system integral with the vehicle in which the assembly is installed. When the vehicle is running, its alternator will supply the power used to energize the thermal energy exchanger and the fan. The power drawn by these components does not affect the alternator""s ability to provide power to the other electrical components of the vehicle or to charge the battery.
When the motor is turned off, there may still be instances in which it is desirable to continue to energize the components of the temperature-conditioned container. For example, on a summer day, an individual may store medicine or food product in the container that should be kept cool. Once the motor is off, the power to energize the thermal energy exchanger and the fan must come from the vehicle""s battery. A disadvantage of this arrangement is that these components may excessively drain the charge stored in the battery. If this event occurs, the possibility arises that, when the persons return to the vehicle, the battery may not have enough power to actuate the vehicle""s starter motor.
More importantly, sudden shutoff of power to the thermoelectric energy exchanger causes abrupt thermal changes or thermal shock that can shorten the working life and efficiency of thermoelectric exchangers or modules. Stress or damage can be caused by different rates of expansion and contraction with respect to temperature in the component materials of the thermoelectric modules.
One object of the invention is to provide a circuit for dampening thermal shock to a thermoelectric energy exchanger for heating or cooling an insulated compartment in a vehicle. Such a circuit dampens thermal shock to the thermoelectric modules and provides gradual thermal transitions to extend the life of the thermoelectric modules.
Another object of the invention is to dampen thermal shock to the thermoelectric energy modules during defrost cycles for a refrigerator or cooler in a vehicle, such as a truck.
This invention is related to a temperature-conditioned container assembly for an insulated container in a vehicle. The assembly includes an insulated container that defines a compartment for storing objects to be kept warm or cold. A heat exchanger plate has a first end disposed in the insulated compartment and a second end that extends away from the compartment. A thermoelectric energy module has first and second faces, the first facing being thermally coupled to the second end of said heat exchanger plate.
A drive circuit connected to a vehicle power source receives power to operate the thermoelectric energy module and to operate a fan motor. The drive circuit drives the thermoelectric energy module with a decaying output signal for a predetermined time to prevent damage to said thermoelectric energy module after the vehicle is shut down.
The assembly of this invention is also constructed so that a separate circuit supplies power to the fan. The circuit is designed to ensure that, regardless of the thermal energy exchanger or thermoelectric module being operated in the heating mode or in the cooling mode, and regardless of whether the thermal heat exchanger is operated at full or attenuated power, the proper current is applied to the fan at full power.
The assembly of this invention is further arranged so that the driver of the vehicle only has to pay nominal attention to the on/off state of the assembly when he/she enters and exits the vehicle.
One embodiment of the invention includes a defrost/operating system that provides a pulse width modulated drive signal to the thermoelectric device in a defrost cycle. The pulse width modulated drive signal decays during the beginning of the defrost cycle. After decaying to zero current, the thermoelectric device is not operated for a predetermined time. Finally the defrost/operating system provides an increasing pulse width modulated drive signal to slowly return the thermoelectric device to full operation. In this manner, sudden changes in the operation of the thermoelectric device are avoided.
This embodiment also includes a power protection circuit to prevent damage to any components of the defrost/operating system due to over voltages, transient voltages or the like.